Treeholes are detritus-based communities, and resource quantity and quality play a large role in structuring such communities. The primary resource is leaf litter, but decaying invertebrates also are a resource to treehole inhabitants. These communities are subject to a variety of disturbances, which may affect resources or cause widespread mortality. When dead inhabitants decay, they provide a potentially high-quality resource to survivors or subsequent colonists. We predicted that variation in decaying larvae (0, 7.3, and 29.2 mg/liter) and leaf litter (1, 5, and 10 g/liter) would influence the performance of populations of Aedes triseriatus (Say), the eastern treehole mosquito. We tested this prediction in field mesocosms, which were subjected to a freezing event causing widespread mortality of the scirtid beetle Helodes pulchella Guerin. We then added a cohort of first instar mosquitoes to mesocosms, and we monitored their development from March until June 2005. At the highest leaf litter level, survival, adult mass, and time to complete development were unaffected by decaying scirtids, and they were different from treatments with lower levels of leaf litter. In treatments with 1 and 5 g/liter leaf litter and decaying scirtids, mosquito survival and adult mass were higher than in treatments with 1 and 5 g/liter leaf litter and no decaying scirtids. At 5 g/liter leaf litter, a higher mass of dead scirtids was required to significantly increase adult mass. Faster decay of carcasses and release of limiting nutrients likely spur growth of microorganisms, upon which mosquitoes feed. Invertebrate populations in high-disturbance communities may be subject to high mortality, and mosquitoes hatching after the disturbance will benefit, but only when other resources are limiting.
The effects of predation on water-filled treehole communities in North Carolina were examined using mesocosm experiments and observations in natural treeholes. The presence of the predator Toxorhynchites rutilus and leaf litter abundance were manipulated in mesocosms to examine interactions between resources and predation. Long-term examination of interactions in unmanipulated treeholes provided data on natural variation in water volume and predator density. Toxorhynchites rutilus preys upon two common treehole insects, Aedes triseriatus and Culicoides guttipennis. We predicted that T. rutilus would act as a keystone predator and reduce the density of these dominant species. This would allow other species to coexist and lead to an increase in diversity. We also predicted that effects of predation would be reduced in habitats with high levels of resources, due to either increased refugia or decreased competition. The results did not entirely support the predictions. In both mesocosms and treeholes T. rutilus depressed densities of the most abundant prey type, A. triseriatus. In treeholes, the presence of T. rutilus depressed densities of the midge C. guttipennis, and predator densities were positively associated with insect diversity in treeholes. Strikingly, higher diversity was also associated with high densities of the dominant prey in treeholes. In addition, mesocosms showed no relationship between T. rutilus presence and species diversity. The relationship between the predator and diversity in treeholes appears to be unrelated to predation on the dominant competitors and is instead caused by some other habitat characteristic. While there were effects of resources on densities and diversity in both mesocosms and treeholes, neither of the resources analyzed, leaf litter or water, appear to be the sole characteristic that mutually allows for large populations of T. rutilus and high species diversity. We conclude that though T. rutilus is an aggressive predator, it does not cause an increase in prey species diversity as a keystone predator would. Further research is needed to determine the conditions that favor the presence of predator and high prey diversity.
Treeholes are detritus-based communities, and resource quantity and quality play a large role in structuring such communities. The primary resource is leaf litter, but decaying invertebrates also are a resource to treehole inhabitants. These communities are subject to a variety of disturbances, which may affect resources or cause widespread mortality. When dead inhabitants decay, they provide a potentially high-quality resource to survivors or subsequent colonists. We predicted that variation in decaying larvae (0, 7.3, and 29.2 mg/liter) and leaf litter (1, 5, and 10 g/liter) would influence the performance of populations of Aedes triseriatus (Say), the eastern treehole mosquito. We tested this prediction in field mesocosms, which were subjected to a freezing event causing widespread mortality of the scirtid beetle Helodes pulchella Guerin. We then added a cohort of first instar mosquitoes to mesocosms, and we monitored their development from March until June 2005. At the highest leaf litter level, survival, adult mass, and time to complete development were unaffected by decaying scirtids, and they were different from treatments with lower levels of leaf litter. In treatments with 1 and 5 g/liter leaf litter and decaying scirtids, mosquito survival and adult mass were higher than in treatments with 1 and 5 g/liter leaf litter and no decaying scirtids. At 5 g/liter leaf litter, a higher mass of dead scirtids was required to significantly increase adult mass. Faster decay of carcasses and release of limiting nutrients likely spur growth of microorganisms, upon which mosquitoes feed. Invertebrate populations in high-disturbance communities may be subject to high mortality, and mosquitoes hatching after the disturbance will benefit, but only when other resources are limiting.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.